Patent GB-129364-A (GB)
Title: Improvements in Sound Detectors.
IPC: G01S1/72
Filed: 1917-11-02
Abstract: 129,364. Western Electric Co., Nash, G. H., Penny, G. E. R., Orace, B. B., and Mack, R. A. Nov. 2, 1917. Locating subaqueous sounds.-A directional sound-detecting device is adapted to be towed, completely submerged, in the wake of a ship travelling at normal speeds, the instruments being carried in a stream line casing filled with liquid and having sound transparent walls, whilst means are provided to prevent the transmission of vibrations from the ship through the towing cable. A weight is attached at an intermediate part of the towing cable to maintain the instrument carrier at the desired depth, and electrical conducting wires are passed through the cable from the carrier to the parent ship. The carrier, Fig. 1, comprises a central section 42 filled with liquid and having mounted therein a bi-directional hydrophone 45 and a unidirectional hydrophone 47, together with a depth gauge 49, whilst attached to the ends are conical air chambers 21, 35, the front air chamber 21 being formed with a central passage 44 for the towing cable 66, whilst the rear chamber 35 is provided with vanes or fins 51. The central section 42 is formed with sound-transparent walls comprising thin sheets of nickel silver bedded on thin strips of rubber and secured to wooden stringers mounted on transverse supporting rings 17. Other walls of a soft and pliable nature, and wooden walls when waterlogged are also stated to be transparent to sound. The bidirectional hydrophone, Fig. 8, comprises a circular metal plate or diaphragm 25 thin at the centre and increasing in thickness towards the rim, to which circular rings 23, 24 are attached. At the centre, a microphone button 26 of known type is provided, enclosed in a watertight casing 27 and connected to insulated leads 39, 40 clamped at 31 to the rim and eventually joining the other lead passing through the towing cable. The hydrophone 45 is mounted, as shown in Fig. 11, by spacing rods 115 in a brass ring 107 rotatable about a vertical axis in adjustable pivot bearings 106, 113 in a frame 102 secured by lugs 105 to a base 100. The limiting position of the hydrophone is determined by stops 116. 117. The base 100 comprises an iron casting containing a series of twelve electro-magnetic coils 120<a>, Fig. 15, cooperating with a two-pole armature 120 on the lower pivot member 106 to enable rotary adjustment of the hydrophone to be effected, the coils 120<a> being connected by separate leads to a switch board 152, Fig. 15, on the parent ship. In the arrangement shown in Fig. 11, all metal surfaces, apart from the hydrophone itself, are covered with rubber or other vibration-damping material 118. The uni-directional hydrophone, Fig. 10, is constructed, mounted, and controlled in the same manner as the bi-directional hydrophone and only differs therefrom in that a flat circular plate 93 with raised centre portion 94 is secured by pure rubber.insulated bolts 93<a> to the rim 23, 24 to render the diaphragm 25 inoperative to sound vibrations from the side on which the plate 93 is situated. The depth gauge 49 is operated by water pressure and comprises a collapsible mercury container at the base of a vertical glass tube in which the carbon rods are suspended, the mercury serving electrically to connect the rods at various points as it is forced up the tube. The towing cable 66 passing through the nose of the carrier contains twenty individually insulated conducting wires. Twelve of the wires are connected to the coils 120<a> of the hydrophone-controlling devices, which are connected in series so that the hydrophones operate respectively at rightangles as shown in Fig. 1. Of the remaining wires, two are connected to the depth gauge 49, two each to the microphone buttons 26, Fig. 8, one acts as a common return to the controlling coils 120<a>, and the remaining one is a spare. The conducting and towing cable comprises a central steel wire encased in a layer of vulcanized rubber, around which the twenty conducting wires are spirally wrapped, being then covered with vulcanized rubber. Around this is placed a layer of jute, a layer of steel armouring wires and an outer covering of hemp and bitumen braid. From a winch on the parent ship, the cable is first passed through a towing weight of the form shown in Fig. 6, a length of about fifty-five feet of cable intervening between the weight and the carrier, Fig. 1, when in the water. The towing weight, Fig. 6, comprises a heavy ball 75 with a conical or stream line tail portion 76 and a pivoted frontal segment 81. The cable passes through the ball and the tail portion as shown. the outer covering and the steel armouring wires being first detached from the rear fifty-five feet of the cable which is all pulled through the tail portion 76. The ends of the steel armouring wires are bent into the form of hooks and sealed by white metal in a cup 86 in the connecting nipple 85 on the pivoted segment 81. Thus between the towing weight and the parent ship the pull is taken by the steel armouring wires. When making the connexion, the tail portion 76 of the weight is detached by removing the screws 77, and a short length of the cable 66 at the rear of the ball is uncovered, freeing the twenty conductors and exposing the central steel wire, which ie then severed, the part going towards the parent ship being left spare whilst the rear part communicating with the carrier. Fig. 1, is fitted with a nipple similar to the nipple 55 shown in Fig 4. The cable is fixed in the small end of the tail fitting 76 in the same manner as the rear end of the cable is fixed in the nose of the carrier, Fig. 1. At the entrance to the nose piece of the carrier, as shown in Fig 4, and at the corresponding exit from the tail piece of the towing weight, a tapering spiral protector 63 for the cable is secured by means of a nut 60 secured into a conical thimble 59 attached to the outer casing by screws 61. Behind the nut 60 are a rubber cushion 70, a sleeve or washer 69, a rubber cushion 71, and a second sleeve or washer 72 secured to the casing by screws 73. Between the cushions 70, 71 are held the four feet of a spider 67, the head of which at 68 forms a seating for the nipple 55. In the case of the carrier, the extreme nose of the air-chamber containing the nipple-carrying members is detachable, being secured to the air-chamber casing by joining plates 58. In seating the nipples 55 in the spiders 68 in the carrier and the tail portion of the towing weight, the central core of the cable is exposed by separating the surrounding wires and spacing these equally between the arms of the spider as shown in Fig. 4. In the operation of the device, the hydrophones having been rotated by operation of the controlling switchboard, until the direction of the source of sound has been ascertained, the distance of the source may be determined by a similar method to that described in Specification 13973/15. The method of operation and the manner of communicating information to the navigating bridge, gun stations &c., are described at length in the Specification. In the Provisional Specification, the use of wax and oil as transmitting media in the carrier are described and references are made to the use of amplifiers for very great ranges and filters for eliminating sounds from surface craft.